This invention is directed to highly viscous elastomeric adhesive compositions having improved elasticity at relatively low add-on levels.
Personal care garments often include elasticized portions to create a gasket-like fit around certain openings, such as waist openings and leg openings. Laminates made from conventional elastic strands and elastic attachment adhesive are often used to create such elasticized portions.
One type of elastomeric laminate is a stretch-bonded laminate that includes elastic strands produced from an extruder and bonded to a facing sheet or sheets using a hot melt adhesive. Laminates including pre-made elastic strands can be processed online but require an elastic attachment adhesive with high add-on in order to reduce strand slippage. The cost of making stretch-bonded laminates can be relatively high due to the cost of the facing sheet or sheets, plus the cost of the elastic strands, plus the cost of the adhesive.
Another type of elastomeric laminate can be made using a vertical filament laminate-stretch-bonded laminate (VFL-SBL) process. However, the VFL-SBL process must be in off-line operation due to process complexity.
Additionally, conventional elastic strand laminates can be rough and uncomfortable. Furthermore, such laminates may cause red-marking on a wearer's skin if the fit is too tight and may result in leakage from the garment if the fit is too loose. Instead, elastic laminates made with elastomeric adhesive compositions can be used in the manufacture of such garments to avoid complicated elastic-attachment steps during the garment manufacturing process.
Elastomeric adhesive compositions are multifunctional in the sense that they function as an elastomer in a nonwoven composite while also serving as a hot melt adhesive for bonding substrates. Elastomeric adhesive compositions in the form of elastomeric adhesive films are currently recognized as suitable for use in the manufacture of personal care articles. More particularly, elastomeric adhesive compositions can be used to bond facing materials, such as spunbond, to one another while simultaneously elasticizing the resulting laminate. The resulting laminate can be used to form an elastomeric portion of an absorbent article, such as a region surrounding a waist opening and/or a leg opening. U.S. Pat. No. 6,245,050 issued to Odorzynski et al., incorporated herein by reference in its entirety in a manner consistent with the present document, discloses one such elastomeric adhesive composition applied in a disposable absorbent article. Elastomeric adhesive laminates are typically more gentle and conformable compared to conventional elastic strand laminates made from conventional elastic strands with hot melt elastic attachment adhesive.
Non-woven elastomeric adhesive laminates may require high output of adhesive add-on to achieve a tension target for product application. High add-on of the film laminate may generate a bulky, thick feel and appearance, and high cost. Furthermore, the high adhesive output requirement for the film formation would make on-line processing even more difficult due to the limitation of hot melt equipment output capacity. Additionally, high processing temperatures and relatively low viscosity are often required for use with current grid melter and drum unloader processes. More particularly, known elastomeric adhesive compositions have been limited to a viscosity of 10,000 to 30,000 cps at processing temperatures of 285 to 410 degrees Fahrenheit due to grid melt capability, or less than 70,000 cps at 350 degrees as disclosed in U.S. Pat. No. 6,245,050. High add-on requirements result in high cost, and high processing temperatures result in short pot life (material degradation).
There is a need or desire for an elastomeric adhesive composition that can be used to create elasticized portions of a personal care garment, wherein the composition maintains sufficient elasticity and can be processed at lower temperatures and applied at lower add-on levels conducive to on-line processing.